Abstract
Purpose99mTc-tricarbonyl-nitrilotriacetic acid, [99mTc]Tc(CO)3(NTA), is a new 99mTc-renal radiopharmaceutical with a clearance equal to that of 131I-ortho-iodohippuran, [131I]I-OIH. Our purpose was to compare the performance of [99mTc]Tc(CO)3(NTA) and [99mTc]Tc-MAG3 in patients with suspected obstruction.Methods[99mTc]Tc(CO)3(NTA) was prepared with commercially available NTA ligand and CRS Isolink kit, and isolated by HPLC. Eighteen adult patients referred for diuretic renography received an intravenous injection of approximately 40 mg of furosemide 15 min prior to either [99mTc]Tc(CO)3(NTA) or [99mTc]Tc-MAG3 (mean activity of 47 ± 4.4 MBq). Data were acquired for 24 min followed by an anterior image of the liver and gall bladder and a measure of voided volume. Patients received a second furosemide injection equal to one third of the original dose followed fifteen minutes later by administration of the alternate tracer, mean activity of 320 ± 34 MBq. Clearances were measured using a camera-based technique.ResultsThe clearance of NTA was greater than that of MAG3, 331 ± 146 versus 271 ± 105 mL/min/1.73 m2, respectively, p < 0.0001. The kidney to background ratio for NTA was greater than that of MAG3 for both left and right kidneys, p < 0.001; the 20 min/maximum count ratio was significantly less, p < 0.0001. There was no significant difference in the voiding volumes following NTA and MAG3 administration, 598 ± 237 mL versus 498 ± 170 mL, respectively, p = 0.07. Gall bladder activity was not observed with NTA but was present in 6/17 MAG3 studies. Images and renogram curves were comparable except for two patients where the NTA study excluded obstruction but the MAG3 study suggested an indeterminate or obstructed kidney.ConclusionsUnlike MAG3, NTA is not eliminated via the hepatobiliary track. Moreover, NTA has a higher kidney to background ratio and more rapid clearance than MAG3. These advantages should allow more robust camera-based clearance measurements and may lead to better discrimination between obstructed and non-obstructed kidneys.
Highlights
Unlike MAG3, NTA is not eliminated via the hepatobiliary track
NTA has a higher kidney to background ratio and more rapid clearance than MAG3
DTPA; less MAG3 remains in circulation during the washout period and less is entering the kidney at the time washout is evaluated [6, 7]. 99mTc-tricarbonyl-nitrilotriacetic acid
Summary
Adult and pediatric consensus groups consider 99mTcmercaptoacetyltriglycine, [99mTc]Tc -MAG3 (MAG3) to be superior to 99mTc-diethylenetriaminepentaacetic acid,[99mTc]Tc-DTPA (DTPA), for diuresis renography [1,2,3,4,5].MAG3 has a much higher extraction efficiency thanDTPA; less MAG3 remains in circulation during the washout period and less is entering the kidney at the time washout is evaluated [6, 7]. 99mTc-tricarbonyl-nitrilotriacetic acid, [ 99mTc]Tc(CO)3(NTA) (NTA), is a new tubular tracer with a clearance equal to that of 131I-orthoiodohippuran, [131I]Taylor et al EJNMMI Res (2021) 11:43I-OIH (OIH); in contrast, the clearance of MAG3 is only 50–60% that of OIH [6,7,8,9]. A small percentage of the injected dose of MAG3 is eliminated via the hepatobiliary pathway and that percentage increases as renal function deteriorates [6,7,8,9,10,11]. Because NTA is cleared more rapidly than MAG3 and lacks hepatobiliary elimination, we hypothesized that NTA might be superior to MAG3 in patients with suspected obstruction for the same reasons that MAG3 is superior to DTPA. The objective of this investigation was a direct comparison of NTA and MAG3 in this clinically relevant patient population
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